This application claims the priority benefit of Taiwan application serial no. 91102060, filed Feb. 6, 2002.
1. Field of Invention
The present invention relates to a thin film transistor liquid crystal display (TFT-LCD) pixel structure. More particularly, the present invention relates to a laser repair facilitated pixel structure and repairing method.
2. Description of Related Art
A thin film transistor liquid crystal display (TFT-LCD) mainly includes a thin film transistor (TFT) array substrate board, a color filter array substrate board and a liquid crystal layer. The TFT array substrate board comprises an array of thin film transistors and a pixel electrode for each thin film transistor. The thin film transistor further comprises a gate electrode, a channel layer, a source terminal and a drain terminal. The thin film transistor serves as a switching element for each liquid crystal display cell.
FIG. 1 is a schematic top view of a conventional pixel structure. As shown in FIG. 1, a pixel structure mainly comprises a thin film transistor 101 and a pixel electrode 110. The pixel is controlled through a scan line 102 and a data line 104. The thin film transistor 101 of the pixel structure further includes a gate terminal 102a, a source terminal 104a and a drain terminal 104b. The drain terminal 104a connects electrically with the data line 104. The gate electrode 102a of the thin film transistor 101 connects electrically with the scan line 102. The source terminal 104b of the thin film transistor 101 connects electrically with the pixel electrode 110. Each pixel electrode 110 corresponds with a thin film transistor 101.
When a break 120 on the data line 104 occurs, a repairing step needs to be conducted so that the ends of the data line 104 at the break region 120 are electrically connected back together. Several methods of repairing a severed data line have been developed. One of the methods is explained with reference to FIGS. 2A to 2C below.
FIGS. 2A to 2C are schematic cross-sectional views along line I-Ixe2x80x3 of FIG. 1 showing the steps for repairing a broken data line using a laser beam. A data line 104 having a broken region 120 on the dielectric layer 106 of a substrate board 100 is shown in FIGS. 1 and 2A. The dielectric layer 106 and the gate insulation layer of the thin film transistor 101 are formed together. The data line 104 further includes another dielectric layer 108 formed in the same process of depositing a protective layer between the thin film transistor 101 and the pixel electrode 110.
To carry out a laser repair, openings 200a and 200b are formed in the dielectric layer 108 above the data line 104 near each end of the broken region 120 using a laser as shown in FIG. 2B so that a portion of the data line 104 is exposed. Since the openings 200a and 200b are formed by a laser burning operation, some material from the dielectric layer 108 piles up to form protruding ledges 201 near the upper corners.
As shown in FIG. 2C, a laser chemical vapor deposition (laser CVD) is carried out to form a conductive layer 202 over the interior surface of the openings 200a and 200b and the exposed dielectric layer 108. Through the conductive layer 202, broken ends of the data line 104 within the broken region 120 are reconnected electrically.
Due to the formation of protruding ledges 201 near the upper corners of the openings 200a and 200b, the conductive layer 202 formed by laser CVD also includes a prominent peak or spike there. The pointed peak or spike in the protruding area is electrically conductive and hence may contact with color filter to form a short circuit route. Ultimately, performance of the device is affected. Occasionally, the protrusion 201 may even lead to a short circuit between the upper and lower panel of a liquid crystal display. In addition, if the broken region within the data line 104 is too long, a conventional laser CVD may not bridge the gap reliably. Hence, yield of the laser repair is often compromised.
Accordingly, one object of the present invention is to provide a laser repairing method capable of reconnecting a broken data line without leading to possible subsequent short-circuiting between the upper and lower substrate board of a liquid crystal display panel.
A second object of this invention is to provide a laser repair facilitated pixel structure capable of tackling low yield problem resulting from the appearance of a long broken section on the data line being repaired.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the invention provides a pixel structure on a substrate board. The pixel structure includes a thin film transistor, a scan line, a pixel electrode, a data line, a conductive line, a first dielectric layer and a second dielectric layer. The thin film transistor is formed over the substrate board. The thin film transistor further includes a gate electrode, a source terminal and a drain terminal. The scan line is formed over the substrate board and electrically connected to the gate electrode. The pixel electrode is formed over the substrate board and positioned next to the thin film transistor. The data line is formed over the substrate board and electrically connected to the pixel electrode via the source/drain terminals. The conductive line is formed underneath the data line. The conductive line has a connective region and a repair section at each end of the connective region. The repair sections protrude over the data line covered range. The repair section at each end of the conductive line may form on the same side as the data line or on the opposite side of the data line. Alternatively, the conductive line may be designed to have a width greater than the data line so that the conductive line outside the data line covered area can also serve as part of the repair section. The first dielectric layer is formed over the substrate board for electrically isolating the conductive line from the data line. The second dielectric layer is also formed over the substrate board to cover the data line. The two repair sections at each end of the conductive line within the pixel structure serve as areas for laser repair according to this invention.
When a break in the data line occurs, the broken data line is repaired by carrying out the following steps. First, the first dielectric layer and the second dielectric layer above the two repair sections are burnt away using a laser beam to form a first opening and a second opening that expose the data line and repair section. Thereafter, a laser chemical vapor deposition is carried out to form a conductive layer over the exposed surface inside the first opening and the second opening. Hence, the two repair sections and the data line are electrically connected. Through the special structural design between the conductive line and the repair sections, the data line can be easily repaired.
This invention provides an alternative pixel structure on a substrate board. The pixel structure includes a thin film transistor, a scan line, a pixel electrode, a data line, a conductive line, a conductive structure, a first dielectric layer and a second dielectric layer. The thin film transistor is formed over the substrate board. The thin film transistor further includes a gate electrode, a source terminal and a drain terminal. The scan line is formed over the substrate board and electrically connected to the gate electrode. The pixel electrode is formed over the substrate board and positioned next to the thin film transistor. The data line is formed over the substrate board and electrically connected to the pixel electrode via the source/drain terminals. The conductive line is formed underneath the data line. The conductive line has a connective region. Each end of the connective region of the conductive line has a contact section and a repair section. The contact section and the repair section protrude over the data line covered range. The contact section and the repair section at each end of the conductive line may form on the same side as the data line or on the opposite side of the data line. Alternatively, the conductive line may be designed to have a width greater than the data line so that the conductive line outside the data line covered area can also serve as part of the repair section or contact section. The conductive structure is formed over the contact section of the conductive line so that the contact section and the data line are electrically connected. The first dielectric layer is formed over the substrate board for electrically isolating the conductive line from the data line. The second dielectric layer is also formed over the substrate board to cover the data line. The repair section at each end of the conductive line within the pixel structure serves as an area for laser repair according to this invention.
When a break in the data line occurs, the broken data line is repaired according to the following steps. First, the first dielectric layer and the second dielectric layer above the repair section is burnt away using a laser beam to form an opening that exposes the data line and repair section. Thereafter, a laser chemical vapor deposition is carried out to form a conductive layer over the exposed surface inside the opening. Hence, the repair section and the data line are electrically connected. Through the special structural design between the conductive line, the contact section, and the repair section, the data line can be easily repaired.
This invention also provides a laser repair method. First, a substrate board is provided. The substrate board includes a distributing wire having a broken region and a dielectric layer that covers the distributing wire. To repair the broken distributing wire, an opening is formed in the dielectric layer within the broken region by laser burning. The opening exposes not only the broken region, but also exposes a portion of the distributing wire at each end of the broken region. Thereafter, a laser chemical vapor deposition is carried out to form a conductive line over the exposed broken region and the broken ends of the distributing wire so that the broken distributing wire is electrically reconnected through the conductive line.
The laser repair method according to this invention is capable of preventing the formation of spikes that may lead to point electric discharge or short-circuiting between the upper and lower substrate board of a liquid crystal display panel.
In a first embodiment of the laser repair facilitated pixel structure and repairing method according to this invention, the repair conductive line and the scan lines are formed in the same process and both ends of the conductive line are designed to be a laser repair region. Hence, any broken data line can be repaired within the small area of the two laser-repair regions. For a larger broken wire, the repairing process will not directly affect production.
In a second embodiment of the laser repair facilitated pixel structure and repairing method according to this invention, the repair conductive line and the scan lines are formed in the same process. Moreover, one end of the conductive line is electrically connected to the data line through a conductive structure while the other end of the conductive line is designed to be a laser-repair region. Hence, any broken data line can be repaired within the small area of a single laser-repair region. For a larger broken wire, the repairing process will not directly affect production.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.